The present invention is directed to an apparatus and method for estimating the expired portion of the expected total service life of a mercury vapor lamp, and more particularly, to an apparatus and method for estimating the expired portion of the expected total service life of a mercury vapor lamp based upon the time the lamp is electrically energized.
Many fluorescence microscopes use mercury vapor lamps for conducting various medical and scientific tests involving the use of fluorescent dyes. Mercury vapor lamps radiate intense ultraviolet radiation and have extremely high luminance in the visible spectral range. A sample to be tested is placed on a microscope stage and irradiated with an ultraviolet light source, such as a mercury vapor lamp. Ultraviolet light has a wavelength which falls in the range of 280 to 400 nm. If the sample has absorbed the fluorescent dye, the ultraviolet source excites the molecules in the dye and a longer wavelength is fluoresced off. The longer wavelength can be seen by the human eye and indicates that the sample has tested positive.
The average service life for a mercury vapor lamp is approximately 100 or 200 hours depending upon the type of lamp used. However, short-term uses of the lamp, i.e., less than two hours, can result in a shorter overall service life of the lamp. This is due to the high voltage initially required cause an arc discharge in the surrounding gas and creates the heat necessary required to vaporize the mercury in the lamp. Many problems can occur if the mercury vapor lamp is not changed prior to the termination of its service life. As the lamp reaches the end of its service life, the ultraviolet radiation drops off, but the lamp still gives off bright white light which leads unwary users to assume that the lamp is still good. Furthermore, when the lamp completely burns out it tends to explode, dispersing quartz particles and mercury vapor around the microscope and work area potentially causing damage to the microscope and injury to a user or other persons in the vicinity. In addition, the work area must be immediately evacuated and then thoroughly cleaned resulting in significant down time for the microscope.
There is a need for an apparatus or method which is capable of accurately determining when the expected service life for a lamp, particularly a mercury vapor lamp, is approaching or has reached expiration. The apparatus should include a display that can be reset when a new lamp is installed. The apparatus should keep a running total of whenever the lamp is switched on and maintain the elapsed time in memory between uses independent of the presence of power. The apparatus should also be able to proportionally determine and account for initial uses of the lamp, i.e., when the lamp is first turned on, and prolonged uses, i.e., over a significant period of time, and should take into account the shortened lamp life caused by short-term use.